For more than fifty years plug baffle devices used in injection molds have been produced by soldering cut-to-length, flat bar stock onto the flat end of a standard, commercially available threaded plug, the flat stock forming a fin-like blade to direct the flow of coolant flow in a coolant passage of a mold. Commercially available standard pipe plugs are manufactured to dimensions according to the American Standard Taper Pipe Thread System for the purpose of sealing tapered pipe thread holes. They are currently used in plug baffle devices due to their availability and low cost. Plug baffle devices are typically made of brass due to its preferable qualities of corrosion resistance and heat expansion. Currently-available plug baffle devices typically have Allen-head wrench sockets extending longitudinally into their plug bases.
Brass pipe plugs are produced by a cold-forming process. Brass cannot be heat treated, but can be work-hardened. In the cold-forming process, a brass plug is work-hardened by the deformation or movement of material. In one stroke, a brass plug is forged from a round blank into its finished shape. Threads on the plug are then formed in a secondary roll threading operation. This formed plug is, therefore, in a work-hardened condition.
With this background in mind, it is noted that typical plug baffle devices have three specific drawbacks:
First, brass is susceptible to annealing when subjected to soldering temperatures and, upon soldering attachment of the fin-like blade to the base member, such annealing softens the brass. This creates a weak hex wrench socket that is subject to rounding or stripping out when substantial torque is applied.
Second, current plug baffle devices have shallow Allen-wrench sockets. This is due to the fact that commercially-available plugs, including those used in plug-baffle devices, are designed simply to plug holes without obstructing fluid flow. The solder joint surface of the plug portion of such typical plug baffle device is typically flat, with the result that there is nothing to accommodate any deeper wrench socket.
Third, the use of soldering for attachment of the plug baffle blade to the plug portion of the typical plug baffle device means that experienced operators are required for assembly of such devices; indeed, a high level of soldering skill is necessary to meet the typical tight tolerances within mold cooling chambers and the requirements of perpendicular attachment and precise rotational concentricity.
In operation, tapered threaded plug bases of plug baffle devices are threaded into corresponding mold ports until tight. The torque applied is enough to provide leak-free installation. Then, the plugs must be turned further (over-torqued) to align properly the blade with respect to the coolant flow within the chamber. This is due to the fact that pipe plugs cannot be torqued tightly and then reversed, since this would lead to possible leakage. Hence, plug baffles cannot be “backed up” to align the blade within the chamber.
When plug baffle devices are subjected to high heat during molding operations, the brass plug portions, which are of course subject to thermal expansion, become even more tightly seated in their respective ports. Moreover, any pipe dope or thread lubricant often disintegrates by virtue of the heat of molding operations. Thus, there is a high rate of seizing or sticking of the plugs to the ports and a high rate of damage to seized plugs in attempting removal when necessary for cleaning, maintenance, or replacement purposes. The high levels of torque required to remove plug baffle devices in these cases often result in plugs having to be drilled out for removal. This drill-out procedure results in significant cost, along with downtime for the injection-mold or die-casting die.
A plug baffle device that is able to withstand higher installation torque and is less susceptible to failure upon removal would be an important improvement in the art.